Put your car keys down: Just because there's only one egg left in the carton doesn't mean you need to dash to the store in a last-minute baking emergency. The perfect substitution may be right under your nose (or more specifically, in your kitchen cabinet or fridge).

Baking Powder (double-acting): 1 teaspoon = 1/2 teaspoon cream of tartar + 1/4 teaspoon baking soda

Baking Soda: 1/4 teaspoon = 1 teaspoon baking powder (any acidic ingredients in the recipe will have a more assertive, tangier flavor)

Buttermilk: 1 cup = 1 cup yogurt (not Greek) or 1 cup milk + 1 tablespoon vinegar or lemon juice; let the mixture sit until curdled before using, about 10 minutes

Cake Flour: 1 cup = 1 cup - 2 tablespoons all-purpose flour + 2 tablespoons cornstarch

Self-Rising Flour: 1 cup = 1 cup all-purpose flour + 1 1/2 teaspoons baking powder + 1/4 teaspoon salt

Cream of Tartar: large pinch to 1/4 teaspoon = 1/2 teaspoon lemon juice

Dutch Process Cocoa Powder: 1/2 cup = 1/2 cup natural cocoa + replace the baking powder in the recipe with half the amount of baking soda

Natural Cocoa Powder: 1/2 cup = 1/2 cup Dutch process cocoa + replace the baking soda in the recipe with twice the amount of baking powder

Eggs: 1 egg = 3 tablespoons mayonnaise or 1 tablespoon ground flaxseed + 3 tablespoons water; let sit 5 minutes before using. Exception: Do not substitute for any recipe that uses whipped egg whites.

Half-and-Half: 1 cup = 1/2 cup whole milk + 1/2 cup heavy cream

Heavy Cream: 1 cup = 1 cup whole milk + 1 tablespoon melted butter

Pumpkin Pie Spice: 1 teaspoon = 1/2 teaspoon ground cinnamon + 1/4 teaspoon ground ginger + 1/8 teaspoon ground clove + 1/8 teaspoon freshly grated nutmeg

Iodized Salt: 1/2 teaspoon = 3/4 teaspoon kosher salt

Kosher Salt: 1/2 teaspoon = 1/4 teaspoon iodized salt

Semisweet Chocolate: 1 ounce = 3 tablespoons cocoa powder + 3 tablespoons granulated sugar + 1 tablespoon oil or melted butter

Dark Brown Sugar: 1 cup = 1 cup granulated sugar + 2 tablespoons molasses or 1 cup light brown sugar

Light Brown Sugar: 1 cup = 1 cup granulated sugar + 1 tablespoon molasses or 1 cup dark brown sugar

Lemon Juice: 1 teaspoon = 1/2 teaspoon apple cider vinegar

Sour Cream: 1 cup = 1 cup plain yogurt

Vanilla Extract: 1 teaspoon = 1 teaspoon bourbon or rum

Whole Milk: 1 cup = 1 cup skim or low-fat milk + 2 tablespoons melted butter

Yogurt: 1 cup = 1 cup sour cream